From: Cedric Le Goater <clg@fr.ibm.com>
Subject: [RFC][PATCH 6/6]: Enable unsharing pid namespace.

Enable unsharing of pid namespace - i.e allow creating and using
a new pid namespace and attaching multiple struct pid_nrs per
process, one for each namespace.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>

---
 include/linux/sched.h |    1 +
 kernel/fork.c         |   22 ++++++++++++++++++----
 kernel/nsproxy.c      |    5 ++++-
 kernel/pid.c          |   18 ++++++++++++++++++
 4 files changed, 41 insertions(+), 5 deletions(-)

Index: lx26-20-mm2b/kernel/pid.c
===================================================================
--- lx26-20-mm2b.orig/kernel/pid.c	2007-03-09 14:56:53.000000000 -0800
+++ lx26-20-mm2b/kernel/pid.c	2007-03-09 15:03:05.000000000 -0800
@@ -546,6 +546,24 @@ void free_pid_ns(struct kref *kref)
 	struct pid_namespace *ns;
 
 	ns = container_of(kref, struct pid_namespace, kref);
+
+	if (ns != &init_pid_ns) {
+		/* BEGIN: to be removed soon */
+		int i;
+		int nr_free = atomic_read(&ns->pidmap[0].nr_free);
+
+		BUG_ON( nr_free != (BITS_PER_PAGE - 1));
+
+		if (unlikely(PIDMAP_ENTRIES != 1)) {
+			for (i = 1; i < PIDMAP_ENTRIES; i++) {
+				nr_free = atomic_read(&ns->pidmap[i].nr_free);
+				BUG_ON(nr_free != BITS_PER_PAGE);
+			}
+		}
+		/* END: to be removed soon */
+		kfree(ns->pidmap[0].page);
+	}
+
 	kfree(ns);
 }
 
Index: lx26-20-mm2b/include/linux/sched.h
===================================================================
--- lx26-20-mm2b.orig/include/linux/sched.h	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/include/linux/sched.h	2007-03-09 14:56:53.000000000 -0800
@@ -26,6 +26,7 @@
 #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
 #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
 #define CLONE_NEWIPC		0x08000000	/* New ipcs */
+#define CLONE_NEWPID		0x10000000	/* New pid namespace */
 
 /*
  * Scheduling policies
Index: lx26-20-mm2b/kernel/fork.c
===================================================================
--- lx26-20-mm2b.orig/kernel/fork.c	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/kernel/fork.c	2007-03-09 15:05:39.000000000 -0800
@@ -57,6 +57,7 @@
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
+#include <linux/pid_namespace.h>
 
 /*
  * Protected counters by write_lock_irq(&tasklist_lock)
@@ -1609,6 +1610,7 @@ asmlinkage long sys_unshare(unsigned lon
 	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
 	struct uts_namespace *uts, *new_uts = NULL;
 	struct ipc_namespace *ipc, *new_ipc = NULL;
+	struct pid_nr *new_pid_nr = NULL;
 
 	check_unshare_flags(&unshare_flags);
 
@@ -1616,7 +1618,7 @@ asmlinkage long sys_unshare(unsigned lon
 	err = -EINVAL;
 	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
 				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
-				CLONE_NEWUTS|CLONE_NEWIPC))
+				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID))
 		goto bad_unshare_out;
 
 	if ((err = unshare_thread(unshare_flags)))
@@ -1637,18 +1639,20 @@ asmlinkage long sys_unshare(unsigned lon
 		goto bad_unshare_cleanup_semundo;
 	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
 		goto bad_unshare_cleanup_uts;
+	if ((err = unshare_pid_ns(unshare_flags, &new_pid_nr)))
+		goto bad_unshare_cleanup_ipc;
 
-	if (new_ns || new_uts || new_ipc) {
+	if (new_ns || new_uts || new_ipc || new_pid_nr) {
 		old_nsproxy = current->nsproxy;
 		new_nsproxy = dup_namespaces(old_nsproxy);
 		if (!new_nsproxy) {
 			err = -ENOMEM;
-			goto bad_unshare_cleanup_ipc;
+			goto bad_unshare_cleanup_pid;
 		}
 	}
 
 	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
-				new_uts || new_ipc) {
+				new_uts || new_ipc || new_pid_nr) {
 
 		task_lock(current);
 
@@ -1696,12 +1700,22 @@ asmlinkage long sys_unshare(unsigned lon
 			new_ipc = ipc;
 		}
 
+		if (new_pid_nr) {
+			pid = task_pid_ns(current);
+			set_task_pid_ns(current, new_pid_nr->pid_ns);
+			new_pid_nr = NULL;
+		}
+
 		task_unlock(current);
 	}
 
 	if (new_nsproxy)
 		put_nsproxy(new_nsproxy);
 
+bad_unshare_cleanup_pid:
+	if (new_pid_nr)
+		free_pidmap_pid_nr(new_pid_nr);
+
 bad_unshare_cleanup_ipc:
 	if (new_ipc)
 		put_ipc_ns(new_ipc);
Index: lx26-20-mm2b/kernel/nsproxy.c
===================================================================
--- lx26-20-mm2b.orig/kernel/nsproxy.c	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
@@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
 	struct nsproxy *old_ns = tsk->nsproxy;
 	struct nsproxy *new_ns;
 	int err = 0;
+	int ns_all;
 
 	if (!old_ns)
 		return 0;
 
 	get_nsproxy(old_ns);
 
-	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
+
+	if (!(flags & ns_all))
 		return 0;
 
 	new_ns = clone_namespaces(old_ns);
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sukadev@us.ibm.com writes:

> From: Cedric Le Goater <clg@fr.ibm.com>
> Subject: [RFC][PATCH 6/6]: Enable unsharing pid namespace.
>
> Enable unsharing of pid namespace - i.e allow creating and using
> a new pid namespace and attaching multiple struct pid_nrs per
> process, one for each namespace.
>
> Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
>
> ---
>  include/linux/sched.h |    1 +
>  kernel/fork.c         |   22 ++++++++++++++++++----
>  kernel/nsproxy.c      |    5 ++++-
>  kernel/pid.c          |   18 ++++++++++++++++++
>  4 files changed, 41 insertions(+), 5 deletions(-)
>
> Index: lx26-20-mm2b/kernel/pid.c
> ===================================================================
> --- lx26-20-mm2b.orig/kernel/pid.c	2007-03-09 14:56:53.000000000 -0800
> +++ lx26-20-mm2b/kernel/pid.c	2007-03-09 15:03:05.000000000 -0800
> @@ -546,6 +546,24 @@ void free_pid_ns(struct kref *kref)
>  	struct pid_namespace *ns;
>  
>  	ns = container_of(kref, struct pid_namespace, kref);
> +
> +	if (ns != &init_pid_ns) {

A cleaned up version of this would make sense.
We don't need to test that ns != init_pid_ns.  
Maybe BUG_ON(ns == &init_pid_ns);

Or do you foresee freeing the initial pid namespace?


> +		/* BEGIN: to be removed soon */
> +		int i;
> +		int nr_free = atomic_read(&ns->pidmap[0].nr_free);
> +
> +		BUG_ON( nr_free != (BITS_PER_PAGE - 1));
> +
> +		if (unlikely(PIDMAP_ENTRIES != 1)) {
> +			for (i = 1; i < PIDMAP_ENTRIES; i++) {
> +				nr_free = atomic_read(&ns->pidmap[i].nr_free);
> +				BUG_ON(nr_free != BITS_PER_PAGE);
> +			}
> +		}
What makes the first page in the pidmap special?  None of the pages should have
an allocated bit if we are freeing the pid namespace....

> +		/* END: to be removed soon */
> +		kfree(ns->pidmap[0].page);

This is wrong.  While a pid namespace is exists we don't free the page
so you need to loop through all of the pidmap entries and free them.


> +	}
> +
>  	kfree(ns);
>  }
>  
> Index: lx26-20-mm2b/include/linux/sched.h
> ===================================================================
> --- lx26-20-mm2b.orig/include/linux/sched.h 2007-03-09 14:56:12.000000000 -0800
> +++ lx26-20-mm2b/include/linux/sched.h	2007-03-09 14:56:53.000000000 -0800
> @@ -26,6 +26,7 @@
>  #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
>  #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
>  #define CLONE_NEWIPC		0x08000000	/* New ipcs */
> +#define CLONE_NEWPID		0x10000000	/* New pid namespace */

Good.  Although it may make sense to submit this as a separate patch.  We
should be able to reserve the number now.

> Index: lx26-20-mm2b/kernel/fork.c
> ===================================================================
> --- lx26-20-mm2b.orig/kernel/fork.c	2007-03-09 14:56:12.000000000 -0800
> +++ lx26-20-mm2b/kernel/fork.c	2007-03-09 15:05:39.000000000 -0800
> @@ -57,6 +57,7 @@
>  #include <asm/mmu_context.h>
>  #include <asm/cacheflush.h>
>  #include <asm/tlbflush.h>
> +#include <linux/pid_namespace.h>

I don't see do_fork support only unshare support which seems completely
backwards to me.

> @@ -1609,6 +1610,7 @@ asmlinkage long sys_unshare(unsigned lon
>  	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
>  	struct uts_namespace *uts, *new_uts = NULL;
>  	struct ipc_namespace *ipc, *new_ipc = NULL;
> +	struct pid_nr *new_pid_nr = NULL;
>  
>  	check_unshare_flags(&unshare_flags);
>  
> @@ -1616,7 +1618,7 @@ asmlinkage long sys_unshare(unsigned lon
>  	err = -EINVAL;
>  	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
>  				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
> -				CLONE_NEWUTS|CLONE_NEWIPC))
> +				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID))
>  		goto bad_unshare_out;
>  
>  	if ((err = unshare_thread(unshare_flags)))
> @@ -1637,18 +1639,20 @@ asmlinkage long sys_unshare(unsigned lon
>  		goto bad_unshare_cleanup_semundo;
>  	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
>  		goto bad_unshare_cleanup_uts;
> +	if ((err = unshare_pid_ns(unshare_flags, &new_pid_nr)))
> +		goto bad_unshare_cleanup_ipc;
>  
> -	if (new_ns || new_uts || new_ipc) {
> +	if (new_ns || new_uts || new_ipc || new_pid_nr) {
>  		old_nsproxy = current->nsproxy;
>  		new_nsproxy = dup_namespaces(old_nsproxy);
>  		if (!new_nsproxy) {
>  			err = -ENOMEM;
> -			goto bad_unshare_cleanup_ipc;
> +			goto bad_unshare_cleanup_pid;
>  		}
>  	}
>  
>  	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
> -				new_uts || new_ipc) {
> +				new_uts || new_ipc || new_pid_nr) {
>  
>  		task_lock(current);
>  
> @@ -1696,12 +1700,22 @@ asmlinkage long sys_unshare(unsigned lon
>  			new_ipc = ipc;
>  		}
>  
> +		if (new_pid_nr) {
> +			pid = task_pid_ns(current);
> +			set_task_pid_ns(current, new_pid_nr->pid_ns);
> +			new_pid_nr = NULL;
> +		}
> +
>  		task_unlock(current);
>  	}
>  
>  	if (new_nsproxy)
>  		put_nsproxy(new_nsproxy);
>  
> +bad_unshare_cleanup_pid:
> +	if (new_pid_nr)
> +		free_pidmap_pid_nr(new_pid_nr);
> +
>  bad_unshare_cleanup_ipc:
>  	if (new_ipc)
>  		put_ipc_ns(new_ipc);
> Index: lx26-20-mm2b/kernel/nsproxy.c
> ===================================================================
> --- lx26-20-mm2b.orig/kernel/nsproxy.c	2007-03-09 14:56:12.000000000 -0800
> +++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
> @@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
>  	struct nsproxy *old_ns = tsk->nsproxy;
>  	struct nsproxy *new_ns;
>  	int err = 0;
> +	int ns_all;
>  
>  	if (!old_ns)
>  		return 0;
>  
>  	get_nsproxy(old_ns);
>  
> -	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
> +	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
> +

This doesn't quite seem to make sense why the extra intermediate variable?

> +	if (!(flags & ns_all))
>  		return 0;
>  

Eric
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Eric W. Biederman [ebiederm@xmission.com] wrote:
| sukadev@us.ibm.com writes:
| 
| > From: Cedric Le Goater <clg@fr.ibm.com>
| > Subject: [RFC][PATCH 6/6]: Enable unsharing pid namespace.
| >
| > Enable unsharing of pid namespace - i.e allow creating and using
| > a new pid namespace and attaching multiple struct pid_nrs per
| > process, one for each namespace.
| >
| > Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
| > Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
| >
| > ---
| >  include/linux/sched.h |    1 +
| >  kernel/fork.c         |   22 ++++++++++++++++++----
| >  kernel/nsproxy.c      |    5 ++++-
| >  kernel/pid.c          |   18 ++++++++++++++++++
| >  4 files changed, 41 insertions(+), 5 deletions(-)
| >
| > Index: lx26-20-mm2b/kernel/pid.c
| > ===================================================================
| > --- lx26-20-mm2b.orig/kernel/pid.c	2007-03-09 14:56:53.000000000 -0800
| > +++ lx26-20-mm2b/kernel/pid.c	2007-03-09 15:03:05.000000000 -0800
| > @@ -546,6 +546,24 @@ void free_pid_ns(struct kref *kref)
| >  	struct pid_namespace *ns;
| >  
| >  	ns = container_of(kref, struct pid_namespace, kref);
| > +
| > +	if (ns != &init_pid_ns) {
| 
| A cleaned up version of this would make sense.
| We don't need to test that ns != init_pid_ns.  
| Maybe BUG_ON(ns == &init_pid_ns);

Yes. It should be a BUG_ON().
| 
| Or do you foresee freeing the initial pid namespace?

No.

| 
| 
| > +		/* BEGIN: to be removed soon */
| > +		int i;
| > +		int nr_free = atomic_read(&ns->pidmap[0].nr_free);
| > +
| > +		BUG_ON( nr_free != (BITS_PER_PAGE - 1));
| > +
| > +		if (unlikely(PIDMAP_ENTRIES != 1)) {
| > +			for (i = 1; i < PIDMAP_ENTRIES; i++) {
| > +				nr_free = atomic_read(&ns->pidmap[i].nr_free);
| > +				BUG_ON(nr_free != BITS_PER_PAGE);
| > +			}
| > +		}
| What makes the first page in the pidmap special?  None of the pages should have
| an allocated bit if we are freeing the pid namespace....

It doesn't need to be special.

| 
| > +		/* END: to be removed soon */
| > +		kfree(ns->pidmap[0].page);
| 
| This is wrong.  While a pid namespace is exists we don't free the page
| so you need to loop through all of the pidmap entries and free them.

Yes. I started out doing the opposite of clone_pid_ns(), but you are
right we should free all pidmap entries here.

alloc_pidmap() pages allocates pages if number of concurrent processes
exceed PAGE_SIZE * 8 (32K for 4K pagesize). But free_pidmap() does not
free them when the number of processes drops below 32K again. I guess
that could cause thrashing when number of processes hovers around 32K.

| 
| 
| > +	}
| > +
| >  	kfree(ns);
| >  }
| >  
| > Index: lx26-20-mm2b/include/linux/sched.h
| > ===================================================================
| > --- lx26-20-mm2b.orig/include/linux/sched.h 2007-03-09 14:56:12.000000000 -0800
| > +++ lx26-20-mm2b/include/linux/sched.h	2007-03-09 14:56:53.000000000 -0800
| > @@ -26,6 +26,7 @@
| >  #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
| >  #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
| >  #define CLONE_NEWIPC		0x08000000	/* New ipcs */
| > +#define CLONE_NEWPID		0x10000000	/* New pid namespace */
| 
| Good.  Although it may make sense to submit this as a separate patch.  We
| should be able to reserve the number now.

Ok.

| 
| > Index: lx26-20-mm2b/kernel/fork.c
| > ===================================================================
| > --- lx26-20-mm2b.orig/kernel/fork.c	2007-03-09 14:56:12.000000000 -0800
| > +++ lx26-20-mm2b/kernel/fork.c	2007-03-09 15:05:39.000000000 -0800
| > @@ -57,6 +57,7 @@
| >  #include <asm/mmu_context.h>
| >  #include <asm/cacheflush.h>
| >  #include <asm/tlbflush.h>
| > +#include <linux/pid_namespace.h>
| 
| I don't see do_fork support only unshare support which seems completely
| backwards to me.

fork()/clone() support for pid ns was in a later patch. But we will drop
unshare() of pid ns for now.

| 
| > @@ -1609,6 +1610,7 @@ asmlinkage long sys_unshare(unsigned lon
| >  	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
| >  	struct uts_namespace *uts, *new_uts = NULL;
| >  	struct ipc_namespace *ipc, *new_ipc = NULL;
| > +	struct pid_nr *new_pid_nr = NULL;
| >  
| >  	check_unshare_flags(&unshare_flags);
| >  
| > @@ -1616,7 +1618,7 @@ asmlinkage long sys_unshare(unsigned lon
| >  	err = -EINVAL;
| >  	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
| >  				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
| > -				CLONE_NEWUTS|CLONE_NEWIPC))
| > +				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID))
| >  		goto bad_unshare_out;
| >  
| >  	if ((err = unshare_thread(unshare_flags)))
| > @@ -1637,18 +1639,20 @@ asmlinkage long sys_unshare(unsigned lon
| >  		goto bad_unshare_cleanup_semundo;
| >  	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
| >  		goto bad_unshare_cleanup_uts;
| > +	if ((err = unshare_pid_ns(unshare_flags, &new_pid_nr)))
| > +		goto bad_unshare_cleanup_ipc;
| >  
| > -	if (new_ns || new_uts || new_ipc) {
| > +	if (new_ns || new_uts || new_ipc || new_pid_nr) {
| >  		old_nsproxy = current->nsproxy;
| >  		new_nsproxy = dup_namespaces(old_nsproxy);
| >  		if (!new_nsproxy) {
| >  			err = -ENOMEM;
| > -			goto bad_unshare_cleanup_ipc;
| > +			goto bad_unshare_cleanup_pid;
| >  		}
| >  	}
| >  
| >  	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
| > -				new_uts || new_ipc) {
| > +				new_uts || new_ipc || new_pid_nr) {
| >  
| >  		task_lock(current);
| >  
| > @@ -1696,12 +1700,22 @@ asmlinkage long sys_unshare(unsigned lon
| >  			new_ipc = ipc;
| >  		}
| >  
| > +		if (new_pid_nr) {
| > +			pid = task_pid_ns(current);
| > +			set_task_pid_ns(current, new_pid_nr->pid_ns);
| > +			new_pid_nr = NULL;
| > +		}
| > +
| >  		task_unlock(current);
| >  	}
| >  
| >  	if (new_nsproxy)
| >  		put_nsproxy(new_nsproxy);
| >  
| > +bad_unshare_cleanup_pid:
| > +	if (new_pid_nr)
| > +		free_pidmap_pid_nr(new_pid_nr);
| > +
| >  bad_unshare_cleanup_ipc:
| >  	if (new_ipc)
| >  		put_ipc_ns(new_ipc);
| > Index: lx26-20-mm2b/kernel/nsproxy.c
| > ===================================================================
| > --- lx26-20-mm2b.orig/kernel/nsproxy.c	2007-03-09 14:56:12.000000000 -0800
| > +++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
| > @@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
| >  	struct nsproxy *old_ns = tsk->nsproxy;
| >  	struct nsproxy *new_ns;
| >  	int err = 0;
| > +	int ns_all;
| >  
| >  	if (!old_ns)
| >  		return 0;
| >  
| >  	get_nsproxy(old_ns);
| >  
| > -	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
| > +	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
| > +
| 
| This doesn't quite seem to make sense why the extra intermediate variable?

Will drop ns_all variable.

| 
| > +	if (!(flags & ns_all))
| >  		return 0;
| >  
| 
| Eric
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Cedric Le Goater <clg@fr.ibm.com> writes:

>> | > Index: lx26-20-mm2b/kernel/nsproxy.c
>> | > ===================================================================
>> | > --- lx26-20-mm2b.orig/kernel/nsproxy.c 2007-03-09 14:56:12.000000000 -0800
>> | > +++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
>> | > @@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
>> | >  	struct nsproxy *old_ns = tsk->nsproxy;
>> | >  	struct nsproxy *new_ns;
>> | >  	int err = 0;
>> | > +	int ns_all;
>> | >  
>> | >  	if (!old_ns)
>> | >  		return 0;
>> | >  
>> | >  	get_nsproxy(old_ns);
>> | >  
>> | > -	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
>> | > +	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
>> | > +
>> | 
>> | This doesn't quite seem to make sense why the extra intermediate variable?
>> 
>> Will drop ns_all variable.
>
> well, in the patch reserving the pid namespace clone flags, 
> we could define : 
>
> #define NS_ALL	(CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID)
>
> which is useful in many ways.

Yes.  Especially if we structured it something like:

#ifdef CONFIG_PID_NS
#define CLONE_NEWPID_NSALL CLONE_NEWPID
#else
#define CLONE_NEWPID_NSALL
#endif

#define NS_ALL	(CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID_NSALL)

So we have a natural way of disabling the pid namespace, until we are certain
it is complete and remove it from CONFIG_EXPERIMENTAL

Eric
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> | > Index: lx26-20-mm2b/kernel/nsproxy.c
> | > ===================================================================
> | > --- lx26-20-mm2b.orig/kernel/nsproxy.c	2007-03-09 14:56:12.000000000 -0800
> | > +++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
> | > @@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
> | >  	struct nsproxy *old_ns = tsk->nsproxy;
> | >  	struct nsproxy *new_ns;
> | >  	int err = 0;
> | > +	int ns_all;
> | >  
> | >  	if (!old_ns)
> | >  		return 0;
> | >  
> | >  	get_nsproxy(old_ns);
> | >  
> | > -	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
> | > +	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
> | > +
> | 
> | This doesn't quite seem to make sense why the extra intermediate variable?
> 
> Will drop ns_all variable.

well, in the patch reserving the pid namespace clone flags, 
we could define : 

#define NS_ALL	(CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID)

which is useful in many ways.

cheers,

C.
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